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Author Topic: Immobilizer in Murena 2.2  (Read 6354 times)
Anders Dinsen
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« on: July 19, 2006, 02:03:56 pm »

Danish insurance companies require a three way immobilizer installed in the car to fully insure it. An immobilizer is also a good way the protect the car from theft, so the trouble installing it is well spent.

I'm thinking what is the best way to install that in a 2.2?

The break circuits could connect to:

- Starter solenoid
- Power supply of ignition amplifier
- Fuel supply by a fuel cut off valve.

However, some recommend fitting an electric fuel pump instead of the mechanical pump and since the price of a pump is almost the same as a cut off valve, I am open to this option - and will then just have the immobilizer break the power to it.

But with an electric fuel pump, I would need to install a circuit that stops the fuel pump if the engine stops running - to prevent flooding, especially in case of fire! - Anyone who knows about safe and ready made solutions to this problem Huh

Any input is appreciated!
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Matra_Hans
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« Reply #1 on: July 21, 2006, 12:00:06 pm »

An immobilizer is a good idea being a requirement from the insurance company or not. In my Murena the immobilizer is blocking starter, ignition and the fuel.
On a Murena 2.2 (single carburettor) you do not need to purchase a cut off valve as an electric cut off valve is build into the carburettor. The purpose of this build in shut of valve is to make sure that the engine stops immediately when you switch off the ignition.
However an electric fuel pump is a good idea any way. I installed one my self after my third engine room fire. An electric fuel pump is also an advantage when driving in hot weather as is can flush out any vapour lock in the fuel line, which might make restarting cumbersome in hot weather.
You can get a safety cut off sensor that will cut off fuel supply as an example
http://www.1firsttech.com/data_sheets_pdfs/fco_resettabldash%20_sensors.pdf

Of you can make your own tachometric relay out of a couple of standard relays i.e. the fuel pump will only be running when power is on for the starter and when the generator is producing electricity.

Due to the low height of the car installing any thing under the dashboard in the Murena (or Bagheera) is very cumbersome and a very unpleasant job, so it will be an advantage to install the electronic control box some where else as an example under the drivers seat.

Regards Hans
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Anders Dinsen
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« Reply #2 on: July 21, 2006, 12:32:35 pm »

On a Murena 2.2 (single carburettor) you do not need to purchase a cut off valve as an electric cut off valve is build into the carburettor. The purpose of this build in shut of valve is to make sure that the engine stops immediately when you switch off the ignition.
So that is what the valve on the side of the carb is for.... great, that makes it a bit easier. Thanks.

Quote
However an electric fuel pump is a good idea any way. I installed one my self after my third engine room fire.

How can a fuel pump help avoid a fire?
What fuel pump are you using? I have read good and bad things about different brands Huh I have a feeling some tend to be religious about it, which I'm not - as long as it works reliably Wink

Quote
Of you can make your own tachometric relay out of a couple of standard relays i.e. the fuel pump will only be running when power is on for the starter and when the generator is producing electricity.

Searching the net has shown me that some Audi's has a standard relay unit for it - think it's those with mechanical fuel injection. It should be possible to fit a single relay in the engine room. I know a guy who's very passionate about Porsche 924's - I'll check with him.

I have since learnt that the fuel system with the 2.2 standard carb is a reflow system so that any excess fuel flows back to the tank. So very strictly it is not necessary to cut off the fuel pump when engine stops. I'll just have to remember to turn the ignition off if a fire starts (which I suppose I would anyway).

... anyway - the good news is that I don't need to purchase an expensive cut-off valve to install the immobilizer Cheesy Thanks for your help, Hans! You seem to be always there when I'm in doubt!

- Anders
« Last Edit: July 21, 2006, 12:34:57 pm by Anders Dinsen » Logged

'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Matra_Hans
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Owner of Bagheera, Rancho, Murena & Espace


« Reply #3 on: July 22, 2006, 10:26:40 am »

Hi Anders
Quote from Anders Dienesen
”How can a fuel pump help avoid a fire?”

The mechanical fuel pump on the Murena 2.2 engine is placed on top of the engine on the right hand side. The pump is a membrane pump when the membrane gets old it will start leaking (just a little bit), when the petrol is dripping down from the pump it will hit the exhaust manifold. I think any further elaboration on the consequences of this will not be necessary.

When I got my Murena in 1995 I installed a new fuel pump in order to avoid this problem. However in 2003 the engine died just after driving 50 m. It turned out that fuel supply had been cut as the plastic petrol filter had melted (due to a minor fire that died out by it self) I could not find any leaks so I imagined that the leak had been in the fuel filter.
After a few months this repeated itself. I checked the fuel pump for leaks but could not find any so I changed the fuel filter to a metal type this time and changed all the fuel hoses.
Again after a few months the situation repeated it self. This time I installed an electric fuel pump and a fuel filter with metal casing from a car with fuel injection. After this I have had no further trouble with the fuel supply.
My first engine room fire died by it self. The two fires that followed I had to extinguish with the fire extinguisher I always have in the car and I always replace the fire extinguisher immediately after it has been used.

On my own car I do not have any automatic cut off system for the electric fuel pump. If the engine dies I will cut the ignition.

regards Hans
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Anders Dinsen
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« Reply #4 on: July 23, 2006, 12:59:09 am »

Hans, I have been told just now by Roy of MECUK, that the valve on the carburettor is not a real fuel cut off valve - it only cuts off fuel for idle. Even if it is switched off, it will be possible to get the engine running by depressing the gas pedal slightly. Thanks anyway.

Engine room fires is something one would want to avoid, especially since using the extinguisher is problematic  - the engine needs a good cleaning afterwards to avoid corrosion problems.

After getting smoke out from under the hood of my Espace I one morning after parking it, I have always had a fire extinguisher in my car (it was hydraulic oil leaking from the high pressure servo hose onto the exhaust manifold - fortunately it dit not catch fire).

- Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
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